Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$219.51	7.121%	$235.1413	$235.14	$235.15	$235.10
Purchase #2	$138.65	4.261%	$144.5579	$144.56	$144.55	$144.60
Purchase #3	$241.85	3.485%	$250.2785	$250.28	$250.30	$250.30
Purchase #4	$51.60	10.286%	$56.9076	$56.91	$56.90	$56.90
Purchase #5	$146.74	12.520%	$165.1118	$165.11	$165.10	$165.10
Purchase #6	$111.83	4.545%	$116.9127	$116.91	$116.90	$116.90
Purchase #7	$88.59	9.467%	$96.9768	$96.98	$97.00	$97.00
7 purchase totals =	$998.77		$1,065.8866	$1,065.89	$1,065.90	$1,065.90